The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
As is known in itself, an aircraft propulsion assembly traditionally comprises a turbojet engine housed inside a nacelle.
A nacelle generally has an annular structure comprising an air intake upstream from the turbojet engine, a middle section designed to surround a fan of the turbojet engine and its casing, and a downstream section designed to surround the combustion chamber of the turbojet engine and, if applicable, housing thrust reverser means. It may end with the jet nozzle whereof the outlet is situated downstream from the turbojet engine.
The air intake structure serves to optimize the capture of air necessary to supply the fan of the turbojet engine and channel it toward that fan.
An air intake structure in particular comprises, upstream, a leading edge structure commonly called an air intake “lip.”
The air intake lip captures air and is attached to the rest of the air intake structure, which channels the captured air toward the turbojet engine.
To that end, the rest of the air intake structure has a substantially annular structure comprising an outer surface ensuring the outer aerodynamic continuity of the nacelle and an inner surface ensuring the inner aerodynamic continuity of the nacelle. The air intake lip provides the upstream junction between said two walls.
The entire air intake structure is attached upstream from a middle section of the nacelle and a fan casing.
An air intake lip structure may comprise many components. It traditionally in particular includes an aerodynamic skin that may be made from several sectors clipped together, one or more reinforcing partitions, one or more junction profiles for the partitions or for attachment to the rest of the air intake structure.
Currently, these elements may be made from heterogeneous materials, and in particular from alloys of different metals, typically with a base of aluminum and/or titanium. Certain elements may also be made from composite materials.
Today, these elements must be assembled by fastening. This results in a significant assembly time and a loss of aerodynamic performance related to these fastenings and assemblies.
Also known are so-called laminar nacelles with an air intake structure having an outer continuity improving the aerodynamic performance. Such a structure is in particular described in document FR 2,906,568.
Currently, such a laminar structure may be obtained by grouping together the air intake lip and the outer cowl in one single-piece structure, thereby ensuring the absence of fastening means and an optimized outer aerodynamic surface.
The production of such a single-piece structure is not easy and requires dedicated molds and equipment with a suitable size. It therefore remains expensive. Furthermore, it remains difficult to reconcile, in a same manufacturing technology (single-piece product), a lip structure that can have a significant thickness, and a cowling structure that bears few forces and therefore has a much smaller thickness.